A variety of occlusally retained mouthpieces have been developed by dentists for a number of different purposes. These mouthpieces are assembled and fitted to the teeth in several different ways.
There are two basic methods for fabricating an intraoral occlusally retained mouthpiece, either forming the mouthpiece directly on the teeth or indirectly on a model of the teeth.
Indirect methods typically require the dentist to take impression of the teeth from which plaster models are fabricated. These models are then used to make the mouthpiece in a laboratory setting. The increased cost and time delay to the patient in acquiring such a mouthpiece has influenced dentists to pursue direct intraoral methods of fabrication.
When fabricating a mouthpiece directly, conventionally an ethyl or methyl methacrylate acrylic resin is used. When cured in the laboratory, these acrylics are safe, but when cured directly in a patient's mouth they can be highly irritating and caustic. In addition they may burn the gingival tissue due to the heat generated during curing. Further, such use of acrylics is contraindicated when the patient is pregnant.
To directly fabricate such a mouthpiece, typically the dentist either forms a doughy "rope" of acrylic to be molded onto the teeth during the curing state. The rope is placed on a plastic substrate, pressed against the teeth and cured. The acrylic monomer slightly dissolves the surface of the substrate so that when fully cured a seamless and permanent bond is formed between the shaped acrylic and the substrate.
Other resins, such as thermoplastic resins like ethylene vinyl acetate, are sometimes used. However, these must be softened by heat which may have deleterious effects on the teeth and gums. Other resins generally do not bond well to the plastic substrates used in such mouthpieces. If the bond breaks while the device is in use, choking on the separated parts is possible.
Typical of the indirect fabrication method is that described by Thornton in U.S. Pat. No. 5,755,219. To produce a device for improving breathing, two trays are provided. The trays are filled with an ethylene vinyl acetate precursor, heated to about 150.degree. F. and pressed against the upper and lower teeth and the resin is cured. This resin at this high temperature may cause discomfort and injure the gingival tissue.
A mouthpiece or splint intended to treat conditions such as temporomandibular joint disorder is described by Summer in U.S. Pat. No. 5,173,048. An arch is held to the lower teeth by metal clips and is coated on the upper surface with an uncured dental acrylic. The patient bites against the arch, embedding the upper teeth in the acrylic, which is then cured. The acrylic is likely to provide the problems detailed above.
A dental device for snoring and sleep apnea treatment is described by Kidd et al. in U.S. Pat. No. 5,829,441. Arch trays are filled with a thermoplastic material, such as ethylene vinyl acetate. The trays is heated to about 165 to 185.degree. F., placed in the patient's mouth. The patient bites into the material in the trays and waits for the material to cool and harden. The heat from the material is likely to have negative effects on the teeth and gum tissue.
Thus, there is a continuing need for improved dental mouthpiece material that are not toxic or irritating to the teeth or gums, do not contain harmful chemicals that irritate the gingival tissue or produce fumes or require heat that are disturbing and potentially harmful to the patient, will bond well with convenient substrate materials and may be removed from the teeth while still quite flexible but shape retaining to allow undercuts and the like to be cleaned up prior to full cure to a tough but slightly flexible state.